The present invention relates to a connector for use in mobiles, backlight liquid crystal displays and the like, and more particularly to a connector capable of reliably locking a flexible printed circuit board to the connector when the circuit board has been inserted thereinto.
In general, connectors for use in mobile phones, charge coupled device (CCD) cameras and the like are much thinner and having contacts arranged in extremely narrow pitches (so-called lighter and more compact connector). A connector of one type mainly comprises a housing and contacts, and a flexible printed circuit board is inserted into the housing to bring the circuit board into contact with contact portions of the contacts (so-called “non-zero-insertion force (NZIF)” type). Moreover, another type connector mainly comprises a housing, contacts and a slider so that a flexible printed circuit board is embraced between the housing and the slider (so-called “zero-insertion force (ZIF)” type and “piano touch ” type). Various methods may be envisioned for holding a flexible printed circuit board by means of the housing and the slider. In many cases, there have been constructions in which after a flexible printed circuit board has been inserted into a housing, a slider is inserted into the housing so that the circuit board is pressed against the contacts. Moreover, depending upon customer's demands or specifications and in the case that narrower pitches of contacts are desired, it may be unavoidable that connection portions of contacts should be located on the side of a fitting opening of a housing into which a flexible printed circuit board is inserted.
A housing may be usually formed with a required number of inserting holes for inserting contacts and a fitting opening into which a flexible printed circuit board is inserted.
In general, contacts each comprise a contact portion adapted to contact a flexible printed circuit board, a connection portion to be connected to a substrate or the like, and a fixed portion to be fixed to the housing. These contacts may be fixed to the housing as by press-fitting.
Exemplarily described in the following passages are Japanese Utility Model Application Opened No. H6-60,983/1994 (Patent Literature 1) as a “zero-insertion force (ZIF)” type connector, and Japanese Patent Application Opened No. H13-257,020/2001 (Patent Literature 2) as a “piano touch” type connector. Moreover, Japanese Utility Model Application Opened No. H6-82,783/1994 (Patent Literature 3) will be exemplified as a locking structure for a flexible printed circuit board. Further, Japanese Patent Application Opened No. 2004-221,067 (Patent Literature 4) filed by the applicant of the present case will be exemplified as a locking structure for a flexible printed circuit board.
Patent Literature 1
For example, Japanese Utility Model Application Opened No. H6-60,983/1994 discloses connectors of the “zero-insertion force” type. As can be seen from the “Abstract” of the Japanese Utility Model, this invention relates to a connector with a slider for a printed circuit board for use in a narrow space in an electronic or communication appliance. The slider is formed at ends of both sides with U-shaped arms with their proximal ends fixed to the slider as guiding means when being inserted into a housing. The U-shaped arms are each provided on its opening side with a projection and formed with a notch such that the opening end is visible from the inserting side. The housing is provided at both the ends with projections having an oblique surface adapted to engage the projections of the slider. When the slider together with connection terminals of a flexible printed circuit board is inserted into the housing, the projections of the slider ride over the projections having the oblique surface of the housing so that the opening ends of the U-shaped arms of the slider are temporarily spread outwardly and then returned to their normal positions when the insertion has been completed.
Patent Literature 2
Japanese Patent Application Opened No. H13-257,020/2001 discloses one example of the so-called “piano touch” type connector. With a view to obtaining an accurate positioning of contacts of the disclosed connector relative to patterns of a flexible printed circuit board or flat cable, projections are provided in a row on a line on a terminal block between the contacts. After a flexible printed circuit board or flexible flat cable has been inserted into the terminal block, a slider is moved to urge the circuit board or flat cable against the contacts. At the moment when the circuit board or flat cable is electrically connected to the contacts by the slider in this manner, the projections snap into recesses between patterns of the circuit board or flat cable, thereby ensuring positional coincidence between the contacts and patterns of the circuit board or flat cable.
Patent Literature 3
As a locking structure for a flexible flat cable, the Japanese Utility Model Application Opened No. H6-82,783/1994 discloses a connector. This utility model has an object to provide a connector provided with a slider having claws capable of anchoring even a flat cable reinforced by a rigid reinforcing plate attached to the rear side of the flat cable. In the connector including a housing having contact pins therein and formed with a fitting space into which a flat cable is inserted, and a slider adapted to be inserted into and removed from the fitting space and mounted on the housing to be pivotally movable outside the housing when the slider is removed therefrom, and the slider being forced into the fitting space after the flat cable has been inserted into the fitting space so that the flat cable is electrically connected to the contact pins, the slider is provided on its flat cable abutting surface with anchoring protrusions adapted to be inserted and anchored in anchoring portions formed in both the flat cable and the reinforcing plate attached to the rear face of the flat cable.
Patent Literature 4
According to the Japanese Patent Application Opened No. 2004-221,067, the object of this invention is to provide a connector ensuring a required holding force for a flexible printed circuit board without any defective or failed connection even with less conductors. In the connector detachably fitted with a flexible printed circuit board, including a required number of contacts each having a contact portion to contact the flexible printed circuit board, and a housing holding and fixing the contacts and having a fitting opening into which the flexible printed circuit board is inserted, the circuit board is provided with anchoring portions, and locking members each having an engaging portion adapted to engage said anchoring portion of the circuit board are installed into the housing so that the engaging portions of the locking members are caused to engage the anchoring portions of the circuit board, thereby preventing the circuit board from being removed from the housing, and grooves are provided at positions corresponding to said engaging portions to ensure a more reliable locking.
In recent years, requirements for less conductors such as four to ten conductors have progressively increased according to specifications of customers. A smaller insertion force of the flexible printed circuit board is better, while a larger holding force for the circuit board is better. In this manner, the opposed requirements are imposed on the insertion force and holding force concerning the flexible printed circuit board. In the “non-zero-insertion force (NZIF)” type connector described above, the insertion force and holding force for the flexible printed circuit board depend upon contact pressure (force) of the contacts. In other words, the holding force for the circuit board will be determined by a product of the number of contacts and contact pressure per one contact. When a customer's requirement for the holding force is 5N and the number of conductors is less than 10, it is impossible to obtain the holding force of 5N, resulting in removal of the circuit board causing a defective connection, which is a problem to be solved.
Even with the “zero-insertion force (ZIF)” type connector, that is, the case that after a flexible printed circuit board has been inserted into a housing, the circuit board is urged against contacts by means of a slider, this type only contributes to increase in initial value resulting from the insertion of the slider so that the contact pressure of contacts still has a great influence on the holding force for the circuit board. Therefore, when a customer's requirement for the holding force is 5N and the number of conductors is less than 10, it is still impossible to obtain the holding force of 5N, resulting in removal of the circuit board causing a defective connection, which problem remains to be solved.
Moreover, even with the structure that anchoring protrusions provided on a slider are inserted and anchored into anchoring portions of a flexible flat cable as is the case with the Patent Literature 3, the influence of the contact pressure of contacts is still great because the inserting directions of the slider and the flat cable are substantially the same. Accordingly, when a customer's requirement for the holding force is 5N and the number of conductors is less than 10, it is still impossible to obtain the holding force of 5N, resulting in removal of the circuit board causing a defective connection, which problem could not be solved.
It may be considered to combine the features of the Patent Literatures 2 and 3, that is, to add the locking structure consisting of anchoring portions provided in a flexible printed circuit board and anchoring protrusions provided on a slider as disclosed in the Patent Literature 3 to a connector of the so-called “piano touch” type as disclosed in the Patent Literature 2. Such a connector would be able to acquire a required holding force for a flexible printed circuit board even with less conductors because of difference between the inserting direction of the circuit board and the direction of rotation of the slider. However, as the slider has no elasticity, if the circuit board is forcedly pulled by a force larger than the holding force, the slider or the flexible printed circuit board would be damaged. When a circuit board is unintentionally subjected to external forces, moreover, the circuit board would be usually pulled obliquely upward rather than a direction opposite to the inserting direction of circuit board. In such a case, the direction of the pulling force acting upon the circuit board and the direction of the pivotal movement of the slider are substantially coincident with each other so that frequently a required holding force could not be maintained.
Therefore, the applicant of the present case has proposed a structure provided with grooves at positions corresponding to the engaging portions of the locking members in the Patent Literature 4. Such a structure can obtain a stable holding force more than 3N. In recent years, however, the requirement for more reduced overall height of connectors has become stronger. With the locking members constructed as in the Patent Literature 4, the further reduced overall height would be difficult.